A. Technical Field
The present invention relates to power conversion circuits and, more particularly, to systems, devices, and methods to monitor current in switching-type power conversion circuits that operate in CCM and DCM.
B. Background of the Invention
Electrical systems used in areas such as consumer electronics applications commonly employ switching power regulators to convert a voltage into another voltage that is suitable to operate various electrical devices within the system. Electronic switching-type regulators are particularly useful in reducing size and cost. They are operated mainly in one of two modes, continuous conduction mode (CCM) and discontinuous conduction mode (DCM), also known as skip mode. Generally, in CCM, the inductor current is always positive and does not change polarity, while in DCM the current flowing through the inductive element is set to zero in each cycle. Skip mode operation is a commonly used to enhance efficiency when the switching regulator operates with a fixed switching frequency under light load current conditions.
Oftentimes control circuitry measures and monitors the load current of the switching converter in real-time in order to obtain useful information about the currents flowing through electrical components connected to a given switching converter in a particular application. Numerous existing approaches to monitor current measure load current by sensing the current on one of multiple power FETs, converting it into a voltage signal, and filtering the signal in order to obtain an average DC voltage that is representative of the DC component of the sensed current. One major drawback with these approaches is that, particularly when measuring current in skip mode operation, the current is susceptible to noise caused by on and off switching transitions present in virtually all switching converters. The noise component of the resulting voltage signal can significantly degrade the accuracy of the detected voltage and, thus, negatively affect the accuracy of the current measurement. Existing designs usually require additional blanking circuitry to remove unwanted noise spikes, which limit the duty cycle range of the switching regulator. As a result, while switching converters that operate in CCM, i.e., under heavy load conditions, provide relatively accurate output signals, switching converters provide much less accurate results when operating in DCM.
What is needed are systems and methods that overcome the above-described limitations.